One of many factors limiting integrated circuit (IC) chip performance is the BEOL parasitic coupling between metal wires. Capacitive coupling is often unintended, such as the capacitance between two wires that are next to each other. Often one signal can capacitively couple with another and cause what appears to be noise. To reduce coupling, wires are often separated as much as possible.
In an effort to reduce the BEOL (back end of line) parasitic coupling between metal wires, much effort has been devoted to lower the dielectric constant of BEOL ILD (interlevel dielectric) films. For example, to minimize the back-end-of-line (BEOL) interconnect portion of circuit delay, the conventional SiO2 dielectric (dielectric constant, k=4.0) has been replaced with dense lower-k films (k<3.0). However, for further performance improvement, more parasitic capacitance reduction is required (k<2.5) for high-speed circuits. This has been accomplished using porous low k dielectrics. However, most of the porous materials have relatively weak mechanical properties as compared to dense dielectrics. It is also difficult to integrate these materials with other BEOL module processes. For example, the conventional chemical-mechanical polish process has difficulty in polishing porous dielectric, and the conventional physical vapor deposition (PVD) diffusion barrier deposition technology cannot offer reasonable coverage on the surface of porous dielectrics. On the other hand, due to the adoption of lower-k dielectrics, the long-term reliability of such materials is rapidly becoming one of the most critical challenges for technology development and qualification. Low-k TDDB is commonly considered a critical issue because low-k materials generally have weaker intrinsic breakdown strength than traditional SiO2 dielectrics. This problem is further exacerbated by the aggressive shrinking of the interconnect pitch size due to continuous technology scaling.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.